The long-term objective of this research is to establish ultrasound as a safe, effective, and non-invasive method for assessing fracture risk, an important component in clinical management of osteoporosis. Osteoporosis afflicts over 20 million people in the U.S., responsible for more than 275,000 hip fractures annually. Currently, the primary means for assessment relies on densitometric techniques. These methods subject the patient to ionizing radiation, are relatively expensive, and do not always provide good estimates of bone strength. Ultrasound offers several potential advantages. It is non-ionizing and relatively inexpensive. Moreover, since ultrasound is a mechanical wave and interacts with bone in a fundamentally different manner than electromagnetic radiation, it may be able to provide more accurate estimates of bone strength and fracture risk compared with current densitometric methods. The goal of this research is to develop a new ultrasound system for bone assessment that is not only accurate but also highly reproducible. The system will use the distal forearm as a site of measurement and employ a novel array based parametric signal processing approach which is ideally suited for obtaining high levels of precision. This research should enable the widespread detection of osteoporosis and fracture risk, and will find application not only in the U.S. but worldwide as well. The specific aims in Phase I of this Fast-Track SBIR grant application are to develop a new array-based system for assessing bone in the distal forearm. This will be achieved using computer simulations of ultrasound wave propagation through a set of forearm bones that have been imaged using micro-CT. Following demonstration of feasibility in Phase I, Phase II will then develop a prototype device and test it in a clinical study. The ultimate goal in Phase III is to then commercialize this novel desktop device and to bring it into worldwide use for a simple, safe and effective instrument for fracture risk assessment. As stated by the National Osteoporosis Foundation, osteoporosis is a major public health threat for an estimated 44 million Americans or 55 percent of the people 50 years of age and older. In the U.S., 10 million individuals are estimated to already have the disease and almost 34 million more are estimated to have low bone mass, placing them at increased risk for osteoporosis. While osteoporosis is often thought of as an older person's disease, it can strike at any age. Osteoporosis is responsible for more than 1.5 million fractures annually, including over 300,000 hip fractures and approximately 700,000 vertebral fractures and 250,000 wrist fractures. Notwithstanding these facts, osteoporosis is under-recognized and under-treated. The proposed research should enable bone testing to be done conveniently and safely in a primary care setting. This should lead to earlier detection and treatment and ultimately to reductions in the number of fractures. [unreadable] [unreadable] [unreadable] [unreadable]